This application claims priority to an application entitled xe2x80x9cMethod of Managing a Plurality of Radio Links in Wireless Local Loopxe2x80x9d filed in the Korean Industrial Property Office on Mar. 12, 1999 and assigned Serial No. 99-8196.
1. Field of the Invention
The present invention generally relates to a wireless local loop (WLL), and in particular, to a method of managing a plurality of radio links in the WLL to set up, add, and release the plurality of radio links between a terminal and a base station (BS).
2. Description of the Related Art
A WLL system wirelessly links a wired subscriber terminal to a telephone office. The WLL system is basically the same as a mobile communication system, except for the fixedness of subscriber terminals.
FIG. 1 illustrates a general WLL configuration based on W-CDMA (Wide-band Code Division Multiple Access), which can be applied to any radio system using the WLL as a substitute for a subscriber line between a fixed network and a subscriber. As shown in FIG. 1, the WLL system includes a terminal 20 connected to a subscriber equipment 10 such as a facsimile or a wired telephone, a base station 30 connected to the terminal 20 via a radio link, a base station controller (BSC) 40 connected to the base station 30 by a trunk line, a local exchange (LE) 50 connected to the BSC 40 by a trunk line, and a public switched telephone network (PSTN) 60 for connecting the LE 50 to another network.
A data link layer, being a layer 2 (L2), manages the radio link between the base station 30 and the terminal 20. The data link layer establishes and releases a radio channel in a radio interface between the base station 30 and the terminal 20, and manages the data transmission between them by W-CDMA technology.
In the thus-constituted WLL, if the base station 30 or terminal 20 requests a call set-up, the BSC 40 commands the base station 30 to assign radio resources (radio channel). Then, the data link layer of the base station 30 controls the terminal 20 and assigns the radio resources to the radio interface.
The terminal 20 is connected to at least one subscriber equipment 10 (facsimile, wired telephone, or personal computer). If the terminal 20 is connected to a plurality of subscriber""s equipment 10, a plurality of calls should be set up between the base station 30 and the terminal 20.
When the radio interface is in a single mode, the data link layers of the base station 30 and the terminal 20 assign an extra signaling radio channel for each call every time the call is attempted.
However, when the radio interface is in a multiple mode, a data link layer checks whether a signaling channel already has been assigned to a terminal which attempts a call, and sets up only a new radio link for sharing the assigned channel in the presence of the assigned channel. That is, the multiple-mode data link layer divides one channel into a plurality of radio links using the link Ids, and uses one radio link for each call.
FIG. 2 depicts a message flow for the radio links between the general data link layers in a conventional radio link managing method. If the BSC 40 sends an establish request message APL2_EST_REQ to the base station 30. The base station 30 determines the ID (LID) of a radio link to be established and sends a receive ready message (RR message) including the LID to the terminal 20, in step M120.
After setting up a radio link corresponding to the LID included in the RR message, at step M130, the terminal 20 sends an RR message (ACK RR message) including the LID, indicating acknowledgment to the base station 30. At step M140, upon the receipt of the ACK RR message, the base station 30 sends the BSC 40 an establish confirm message APL2_EST_CNF, notifying the set-up of the radio link with the LID. When the radio link is completely established, the base station 30 and the terminal 20 communicate over the radio link.
If a call is connected between another subscriber linked to the terminal 20 and the base station 30 during the communication, the BSC 40 requests the set-up of an additional radio link to the base station 30. This procedure is called xe2x80x9cadd.xe2x80x9d In this case, at step M150, the BSC 40 sends an add request message APL2_ADD_REQ to the base station 30. At step M160, the base station 30 sends the terminal 20 an RR message including a new LID.
At step M170, the terminal 20 sets up the additional radio link with the new LID and sends an ACK RR message to the base station 30. At step M180, upon receipt of the ACK RR message, the base station 30 sends the BSC 40 an add confirm message APL2_ADD_CONF, notifying that the radio link that the new LID is added.
If calls are released from some or all of the radio links established between the terminal 20 and the base station 30, the BSC 40 sends the base station 30 and the terminal 20 a release request message in step M190. Then, the base station 30 and the terminal 20 release some or all of the established radio links.
However, a problem with the conventional radio link managing method is that if a BSC requests the set-up of a radio link to a base station, the base station cannot find out whether the requested radio link is to be a newly established radio link or an additional radio link (an add). Then, the radio link already established for a certain subscriber equipment is set up for another subscriber equipment, or the established radio link is released, thereby disconnecting a call. Consequently, the radio link management is implemented by influencing an existing call on another established radio link in the conventional method.
It is, therefore, an object of the present invention to provide a multiple radio link managing method in a WLL, wherein the data link layers of a terminal and a base station are able to set up a new radio link, add an extra radio link, and release an established radio link without influencing an existing call.
To achieve the above object, there is provided a method of managing a plurality of radio links in a WLL. In the present invention, the state of each radio link is defined as: (1) L2_NewLid, indicates that establishment of a radio link is requested but not completed; (2) LNK which indicates that a new connection is established to the radio link; and, (3) L3_AddReq, which indicates that the establishment of the radio link is pending. In a method of managing a plurality of radio links between a base station and a terminal according to an aspect of the present invention, the base station receives a radio link establish request message. Then, a data link layer of the base station sets the LNK of a radio link to be established to a logic 1, transmits a request for establishing the radio link to the terminal, receives an acknowledgment from the terminal, notifies a BSC that the radio link is established upon the receipt of the acknowledgrnent, and initiates a service between the terminal and the base station on the established radio link.
In a method of managing a plurality of radio links between a base station and a terminal according to another aspect of the present invention, a data link layer of the base station receives an add request message for a new radio link on a radio link, and checks L2_NewLid and LNK of the new radio link to be added if the data link layer is in a multi-frame established state. If L2_NewLid and LNK are logic 1s, the data link layer adds the new radio link. If L2_NewLid is logic 1 and LNK is logic 0, the data link layer determines that frame errors have occurred and performs an add failure operation. If L2_NewLid is logic 0 and LNK is logic 1, the data link layer performs an add failure operation. If both L2_NewLid and LNK are logic 0s, the data link layer sets both L2_NewLid and LNK of the new radio link to logic 1s and adds the new radio link.
According to a further aspect of the present invention, a method of managing a plurality of radio links between a base station and a terminal a data link layer of the base station receives an add request message for a new radio link on a radio link and checks L2_NewLid and LNK of the new radio link to be added if the data link layer is in an exception recovery state. If L2_NewLid and LNK are logic 1s, the data link layer sets L3_AddReq of the new radio link to 1. If L2_NewLid is 1 and LNK is 0, the data link layer determines that frame errors have occurred and performs an add failure operation. If L2_NewLid is 0 and LNK is 1, the data link layer also performs an add failure operation. If both L2_NewLid and LNK are 0s, the data link layer sets L2_NewLid, LNK, and L3_AddReq of the new radio link to 1s, waits to transit to a multi-frame established state, searches for a radio link with L3_AddReq=1 after the data link layer transits to the multi-frame established state, sets L3_AddReq of the searched radio link to 0, and adds the searched radio link.
According to another aspect of the present invention, a method of managing a plurality of radio links between a base station and a terminal the base station receives a release request message for a radio link. Then, a data link layer of the base station sets LNK of the radio link to be released to 0, transmits a release request message for the radio link to the terminal, receives an acknowledgment from the terminal, and notifies a BSC that the radio link is released upon the receipt of acknowledgment.